二级出水中Fe与腐殖酸共存时的膜污染特性及控制条件研究

发布时间：2018-05-22 13:22

本文选题：超滤膜 + 膜污染　；参考：《西安建筑科技大学》2015年硕士论文

【摘要】：本实验以城市二级出水为主要研究对象,分析了二级出水中所含的有机物和无机金属元素的主要成分,探讨污水中金属铁元素与有机物腐殖酸在不同pH条件下共存时的膜污染行为,同时,对实际二级出水的膜污染进行清洗实验和控制条件研究,为超滤膜技术在水资源再生过程的应用提供理论依据。所得主要结论如下:(1)实验表明,Fe与腐殖酸共存时,随着溶液pH的增大,造成膜污染的主导原因由腐殖酸和铁离子的络合作用转变为氢氧化铁絮体为主的膜污染,再到腐殖酸的排斥力作用为主的膜污染,呈现出先减轻再加重再减轻的趋势,而且污染后的膜用柠檬酸清洗的效果最好。具体结论如下:①低pH值时,铁离子的存在能有效改变腐殖酸污染物在膜表面的沉积形式,加大污染物之间空间距离,提高膜过滤通量;原子力显微镜结果显示低pH时,铁离子的加入降低了污染物和膜之间作用力,进而减小二者的黏附作用,缓解膜通量衰减。②不同pH情况下铁离子的存在状态发生变化,从离子态转化为氢氧化铁,氢氧化铁絮体的产生加重了膜污染,然而,在较强碱性环境中由于腐殖酸本身的羟基和羰基的解离呈负电性,污染物之间相互排斥难以聚合,从而要比中性溶液的过水通量大;微观原子力测定同样得到此结论,较强碱性下污染物与膜之间平均粘附力减小,污染物与膜之间作用变弱,通量有所增大。③从四种清洗剂的清洗效果来看,离子态的铁与腐殖酸的结合造成的膜污染轻容易清洗掉,使得污染膜的不可逆污染减小;而当pH为5、8时,铁离子转化为氢氧化物状态及其与腐殖酸的相互作用使得膜污染加重。随着溶液碱性的不断增加,导致腐殖酸发生解离,所产生的排斥作用会阻止氢氧化铁沉积于膜表面,从而减轻膜污染。原子力形貌图同样显示,不同条件下膜表面粗糙度和污染物形态随pH值的不同而发生变化,其结果与作用力曲线的结果相同。(2)二级出水造成的膜污染是污水中多种污染物相互作用的结果。通过对二级出水进行不同周期的清洗实验,探讨污染物的基本特性和不可逆污染的去除效果。结果表明,周期为5h的清洗实验中,除柠檬酸外,其他三种清洗剂清洗前后通量衰减变化不明显,且清洗剂浓度的增大对过滤通量影响不大。而柠檬酸随着浓度的增大,通量恢复有明显提高,2%柠檬酸四个周期的清洗恢复率都在90%以上,平均通量恢复率为95%;1h周期的膜污染清洗结果表明,四种清洗剂中柠檬酸清洗后通量恢复率是最高的。(3)超滤膜在污水厂实际运行过程中,反洗流量的调节对膜污染的控制有重要作用。此外,在合适的跨膜压差增长情况下进行加药反洗能有效提高膜组件的跨膜压差恢复率。在膜处理系统正常运行的情况下,超滤膜处理系统对浊度、磷酸盐、COD和UV254等二级出水中的污染物去除效果优良,经超滤膜处理后的水均能够达到城市污水再生利用-城市杂用水水质标准(GB18920-2002)。
[Abstract]:The main research object of this experiment is urban two effluent. The main components of organic and inorganic elements in the two grade effluent are analyzed, and the membrane fouling behavior of the metal iron and organic humic acid in the sewage under different pH conditions is discussed. At the same time, the experiment and control of the film pollution of the actual two grade effluent is carried out. The main conclusions are as follows: (1) the main results are as follows: (1) the experimental results show that, when the solution pH increases, the leading cause of membrane fouling is from the complexation of humic acid and iron ion to the membrane fouling of ferric hydroxide floc and then to humus when the Fe and humic acid coexist. The membrane fouling, which is the main effect of the acid repulsive force, presents a tendency to reduce first and then reduce again, and the effect of citric acid cleaning is the best after pollution. The concrete conclusions are as follows: (1) when low pH value, the existence of iron ions can effectively change the deposition form of humic acid pollutants on the surface of the membrane, increase the space distance between pollutants, and improve the membrane The results of the atomic force microscopy show that the addition of iron ions reduces the force between the pollutants and the membrane at low pH, and reduces the adhesion between the two and alleviates the membrane flux attenuation. 2. The existence of iron ions in different pH conditions changes from the ion state to the iron hydroxide, and the formation of the ferric hydroxide floc aggravates the membrane fouling. However, in strong alkaline environment, the dissociation of hydroxyl and carbonyl groups of humic acid itself is negative, and the mutual exclusion between pollutants is difficult to polymerize, and the flux of excess water is larger than that in neutral solution. In the light of the cleaning effect of four kinds of cleaning agents, the membrane pollution caused by the binding of iron and humic acid in the ionic state is easy to be cleaned and the irreversible pollution of the membrane is reduced. When the pH is 5,8, the transformation of iron ions into hydroxides and the interaction with humic acids make the membrane fouling worse. As the solution alkalinity increases, the humic acid is dissociated, which will prevent the iron hydroxide from depositing on the surface of the membrane, thus reducing the membrane fouling. The atomic force morphologies also show that the surface roughness of the membrane and the morphology of the pollutants vary with the pH value under different conditions. (2) the membrane fouling caused by the two grade effluent is the result of the interaction of various pollutants in the sewage. The basic characteristics of the pollutants and the removal effect of the irreversible pollution are discussed through the different cycle cleaning experiments on the two grade effluent. The results show that the cleaning tests of the period of 5h, except for the citric acid, are used for the cleaning of the other three kinds of cleaning agents. The flux attenuation change is not obvious, and the increase of the detergent concentration has little effect on the filtration flux, but the flux recovery of citric acid is obviously improved with the increase of concentration. The recovery rate of 2% citric acid four cycles is above 90% and the average flux recovery rate is 95%; the results of membrane fouling cleaning in 1H cycle show that four kinds of detergent are lemon. The rate of flux recovery is the highest after acid cleaning. (3) during the actual operation process of the ultrafiltration membrane, the regulation of the reverse flux is important for the control of the membrane fouling. In addition, it can effectively improve the recovery rate of the membrane pressure difference in the membrane module under the appropriate growth of the transmembrane pressure difference. The ultrafiltration system has a good effect on the removal of pollutants in the two levels of turbidity, phosphate, COD and UV254. The water after ultrafiltration can reach the standard of urban wastewater reuse - urban water quality standard (GB18920-2002).
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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